Personally, I’d also love them to support Webmention which I think would be generally useful as well. There are obvious use cases for it in addition to an anti-abuse one which I’ve written about before. Perhaps if it were supported and had better anti-troll or NIPSA (Not In Public Site Areas) features folks like Audrey Watters might not block it.
There is the (abandoned?) Hypothesis Aggregator plugin which Nate has worked on a bit that allows a relatively easy PESOS workflow from Hypothes.is to WordPress, but you’re right that it would be nice to have a micropub version that would work for all CMSs.